Electrolytic recording



Oct. 12, 1948. H. G. GREIG ELECTROLYTIC RECGRDING Filed Deo. 3, 1945 l,IN

' Patented Oct. 12, 1948 ELECTROLYTIC RECORDING Harold Grey Greig,Princeton, J assignor to Radio Corporation of America, a corporation ofDelaware Application December 3, 1945, Serial'No. 632,547-

12 Claims.

The present invention relates to the electrolytic production of coloredrecords and particularly to the use in such a method of compositionswhich are designed to give on a light background dark blue gray colorimages which simulate black in color. l

Solomon in his U. S. P. 2,306,471 discloses various methods of producingcolored records by the electrolytic method. lIlhe bes-t of the methodsdisclosed by Solomon from a practical standpoint is that which may betermed the electrolytic diazotization 'and -coupling method. In .thisprocedure, a traveling web or band of lbrous material which has lbeenimpregnated with a diazotizable amine, an ionizable nitrite, anelectrolyte and a coupling component is subjected to electrolysis withthe formation of a diazonium compound yat the anode which subsequentlycouples with the coupling component to produce what is probably an azodyestui. While this method :has many advan- .tages over the previouslyknown method involving the utilization of an electromagneticallycontrolled printer bar, particularly from the standpoint of the speed atwhich the records are made and the wear on the printer bar, itnevertheless presents the diiculty of selecting diazotizable amines andcoupling `components which when chemically united give color imagesapproaching black on a light Ibackground. Many of the diazotizableamines vand azo dye Icoupling components which have been proposed in thepast give dark ycolor images but these are eithertoo lblue, purple orred in color. On the other hand, others which have been selected yielddark -colors but with a -colored background so that there is insuicientcontrast from a practical standpoint in transmission of the record.While many attempts have been made tov select componentsy which whendiazotizedand coupled produce black records on a light background, -tothe best of my knowledge such attempts have to the present time met withconsistent failure.

I have now found that it is possible by the electrolytic diazotizationand coupling method to produce dark images on a stabilized lightbackground if there be employed as the diazotizable paper stainingreaction products.

group and which serves in part as the coupling component also has adecided stabilizing. veilect upon the background of the recordsobtained.

It is accordingly an object of thepresentzginj Vention to provide yacomposition; for theprodum tion of colored records .by electrolyticdiazotization and coupling which insures the formation of colored imagessimulating vblack in color on a light background.

It is a further object of the .present invention to provide a method forproducing electrolytic records in which the color images formed simulateblack in color and are produ-cedlonFalight background. f l

It is a further object of the present invention to provide for theproduction 'of coloredrecords by electrolytic -diazotization andcoupling lwhile using a specific diazotizableamineland 1Vspecificcoupling -components and to vary the shade-of lthe recorded color image`from blue to yellow while adjusting the. proportions of thediazot'izable amine and of the coupling components.

It isla. Afurther object of the present invention to employ a nitrogencontaining organic compound for increasing the darkness of the image ofthe records.

Other and further important objects of the invention will be apparent asthe descriptionproceeds. 'Y

The particular diazotizable amine? contem# plated by thepresentinvention isb'enzidine'- disulfonic acid. YNo otherdiazotizaiblle amine has been found which will Ifunction in the desiredrelationship to yield 4the lblack appearing records on -a lightbackground required herein. As a matter of fact, ii benzidinemonosulfonic acid appears in the composition even as -an impurity, itaiect's the stability of the 1solution by forming Furthermore, suchcompound if present shifts the shade of t-he recorded c-olor towardspurple. Even the isomeric amine a particular aryl diamine disulfonic`acid tant observation which I have made is thatfv the compoundwhichcontains a. reactive methylene blue to brightl yellow. Another and veryimporfV benzidine`2.2'disulfonic acid when present as an yimpuritycauses a shift in the shade of therecord towards purple. Theemploymentof benzidin'e- 3.3disulfonic acid as thediazgoti'zable'v'aminefis accordinglycritical-to the invention.` A l Thenaphthol sulfonic acid couplingcomponent which is employed is abenZoylIfI-acid haviling the following' constitution:

in which X is hydrogen, an acylamino groupl such as acetylarnino,ypropionylamino, benzoylamino, lfuroylamino 'and the like,-alkyl I.suchas methyl, ethyl, propyl, butyLoctyl and the like,

alkoxy ysuch as methoxy, ethoxy, propoxy, butoxy and the like, halogensuch as chlorinebromine and the like, and aryloxysuch as phenoxy and thelike.

Where X is a substituent group, it may be at-y V tache'd at any positionortho, meta-,vA orfrparato the amide linkage in the 8-position of thenaphthol ring. 'Examples of suitablecompoundsare benzoyl Hacid,'benzoylpamino benzoyi H acid,

acetyl-pamino benzoyl H acid, benzoyl maminobenzoyl H acid, toluoyl Hacid; rrr-methoXy-benf Y zoyl H acid, p-phenoXy-benzoyl H acid,Vp-ethyl-V benzoyl H acid, m-butyl-benzoyl H acid, `11a-'chloro- Ybenzoyl H acid, and the like.

' The other 'couplingV cornpoi'u'rd` containing 'the reactive methylenegroup is a diac'etoacetyl. alkylenepolyamine in which the alkylene.chain may tie-interrupted by irnino.` Such compounds: have the followingn stru ctural` formula Qin-which Y isan alkyicnc rcdicarcr such-radica tinterrupted by an imino group. Examples ,ofV

such. 4compounds are diacetoacetyll ethylene diaminec-'dacetoacetylapropylene diamine, diacetoacetyl butylene diamine,diacetoacetyldiethylene triamine, diaoetoacetyl. triethylenetetraminefand the like".

Compounds other than those' vin the aboveclass and i which containa.reactive methylene .group have been tested but for .the most part theresults V*obtained therefrom arernegative in character.

Theoretically, .mono-aceto-acetylfp-phenylene di-Y .amine should vgive amorepronounced change in shade towards black than .the diacetoacetylalkytc 1Y gram m01 cf the nner) tc produce a black record, such recordshows ajgreater tendency tor darken in the VbackgroundY upon filestorage.

' The hue or color of the records is dependent to Y a large extentV uponthe ,proportions of thecomponents "formingfthe dyestuf of the'iinagsthere-y of and thisV is particularly true V'as regards the lcouplingcomponents. The benzidine-3.3disul Afcnic acid is used in the ratio cfabout .02 1:0.'036 5 I vgram mol perliter with the proportions ,ofV thecoupling components as subsequently stated has relatively llittle'eecton the color of Vthe image records. If th'eaymount be decreasedbelow .02. gram mol perA liter, the recordedcolor has a` .strengtnwhichis belowthat required for prac- Nevertheless, legiblel tical recordingsolutions. recordings can still bemade at concentrations below saidlimit of .02flgram rnol per liter. If the quantity Iof .the benzidine35'-disulfonic' acid be increased above ithe upper limit of".036 grammol, the'stability of the background suffers,l ali-` A though hereagain, legible Vvrecord-ings :can be Iliade.

My investigations have 'e'stabl-i-slfie'ditliai-,-l with an amount ofthe diabotizable amineY in thefratio stated, Ythe desired lblack 'imageson a lightfback.- ground'can beobtainedwhile usiiifgth,benz'oyl H .022Vglam mcljpcr liter aud 'che' di'acetcacctyriaikylene polyamine in ,anamount of .029210,05 gram mol'per'liter. I l

If therecording'solution'be Inadefup ith u,the

Y ,beminnen-3.3-disuifcuic. acid Wil-,1uicuiifgga(bcn,-v zoylHacidaslthe 4ciouplirngn component, thejirodlV uct L. which willV beobtained, Aassuming the;couplerv to be bcnzcyi Hfacid, willnavctnclfcilcwin c eb,- able formula;V

This `dyestu Vgives ja brightV 'blue recordgon `a yellow tintedbackground;l Ifv, onth'e'otherlhand, the recording isoluti'o'niisAmaclu'jga with thefbY nfzidine3,3"disulfonic acid and with, Vforexample. diacetoacetyl ethylene diamine `as ,theV ,only couplingcomponent; the '.dyestu whichfisfobtained k has the followingI'Ji'fobableV formul'a Jene polyamines. Unfortunately, ,howeveij, the

solubility of this .compound doesnot .a sufcient quantitvoftheY-s'ame toremain .in soluf non to produce the dcsircdblack shade. while;

it may be employedV in .aclmxture `with thev diace- Ytoacetyl alkylenepolyamine '(say, inan1ounts ranging from ,10 to .'25 grain/moloftheforrner the ben'zoyl H'aid and the4 diacetoacetylgethylene Ydiamine, particularlyin the. proportions statemla ,product will beobtained which. Willcontain a dye-1 stuff` having .either the followingformula;v

Nk 0H SOaNa It appears that when the two coupling components areemployed, a mixture of dyestuffs ensues n in which, however, there isprobably present the product of 'Formula III or IV. Where theproportions are selected as indicated, such product is the majoringredient in Which case the desired blue-gray records are formed. Forinstance, the recorded color obtained when using a mixture of couplingcomponents in said ratio is a gray on white on washed copy and suchcolor under ultraviolet light appears as a bright red on white. Therecorded color on unwashed copy, however, is more nearly black on alight yellow background and under ultraviolet light appears to' be aAstrong black on a yellow background. This difference in color betweenthe washed and the unwashed records Aindicates that two or more colorsare formed during the electrolytic step. It is to be pointed out,however, that there is no indication of the presence o-f a product ofFormula I or of II as these appear blue and bright yellow respectivelyWhen viewed under ultravi-olet light. Despite the fact thatv a mixtureof dyes appears to v'be formed, it is surprising that the mixture doesnot show up a-s a two-tone effect in' recording a picture where agradation in the density of the color is necessary.

It is apparent from what has been'said abo-ye about the proportions ofthe coupling components that by having present an excess of the benzoylH acid or its derivative over the ratios given, the recorded color willbe shifted towards the blue end of the spectrum. Conversely, if therebean excess of the diacetoacetyl ethylene diamine present, the recordedcolor will be shifted towards the yellow region Of the spectrum. By amodification of the expressed ratios, it is as a matter of fact possibleto obtain recorded colors ranging from bright blue through dark blue,blue-gray (almost black), brown, orange brown and bright yellow. Whilethemain purpose of the present invention is to utilize theaforementioned diazotizable amine and mixture of the coupling componentsin a ratio assuring the formation of a record simulating black in color,nevertheless it' is to be understood that the invention in its broadestaspects also contemplates the utilization of mixtures of the aforesaidcoupling components in ratios which will lead toa recorded colorotherthan black.

An indication of the results which ensue when departing from theaforesaid ratio of coupling components may be gathered from thefollowing information. v If, for instance, there be employed .0231 grammol per liter of the benzidinef disulfonic acid with .008 gram mol `perliter of the benzoyl I-I acid compound and .073 gram mol per literv ofthediaeetoacetyl alkylene polyamine,

the record obtained is bright yellow. `Onthe other hand, if there beemployed .0303 gram mol per liter of the benzoyl H acid compound, .025.gram mol per liter of diacetoacetyl alkylene polyt' amine with .0214gram mol per liter of the'benzifv dine-3.3disulfonic acid, therecordobtainedisy a pleasing blue in color.r These proportionsthr'eforegive a general indication of the variations'in color which may beobtained Within the range of hues previously mentioned. i

The importance of the observation that Athe invention contemplates otherproportions of .coupling components than thosel stated is more forciblybrought home by the fact that the di-r d acetoacetyl alkylene polyaminekexerts al dual function in the composition. Thus not only does thiscomponent react with the diazotized benzidine-3.3disulfonic acid informing thecolored record but it also has the surprising capability ofexerting a very strong stabilizing effect'which retards the backgrounddarkening attributable to the benzoyl H acid. This effectis producedeven' when the diacetoacetyl alkylene polyamine is' employed inquantities outside of the ranges serv' ing to produce the blue-gray,simulating black colors. v i

Another feature of the invention, which is of prime significance, is thefinding that ,the darkfl r ness of the color may be considerablyimproved if there be present in the recording solution a quantityfof analiphatic compound containing-a thio amide group in which the nitrogenatom of the amide is disubstituted by hydrogen.- Suitable examples ofCompounds within this category are thiourea, thiosinamine, thiocarbamicacid and the like. These compounds due to the presence ot the NH2 grouptherein have the ability to formsalts with the sulfonic acid groups inthe diazetizable amine and the coupling components. vOn the other hand,it is an accepted fact that the grouping =C=S present in theaforestatedcom# pounds is a very strong chromophoric group. It has notbeenascertained whether the darkening of the color resulting from theutilization of these compounds is attributable either to salt rformationorto the presence of the chromophoric group or both. However, despitethe theory involved, the fact remains that the use of these compoundsdefinitely effects darkening of color and hence they are desirableadjuncts in the recordingfcomposition. The quantity of the 4compoundswhich are to'be used should range from 'about .02 to .0526 gram mol perliter of solution. The other essential components of the composition arean electrolyte to facilitate the. passage of the electrolyzing current,and a water-soluble: metal nitriteto furnish the ions necessary for.

v; tralinorganicsalt such as sodium chloride, so-;

f'stable. Y

*'color is beingrecorded.

'Ifhe currentdensity under theserconditions'may "also vary` considerablyalthough' itihas a mini- Yalllffrfant Color'j'formalf'Ellismillir"rnuirris termed'gthe threshold value and varies with thecomposition of* thefsolution used, High alkalinity; orre'ac'iily.,:oxidized` vorganic I'inter- ,mediates yand the likeincrease` this threshold ""v'alue or'minimum current necessari/'jorfaint color formation. The primary're'quisiteis that the current producea highl enough concentration of hydrogen ions at the surface of thepositive electrode to overcome the initial alkalinity of the wet carrierandallow for nitrousacid formation and -diazotization of thebenzidine-3.3disulfonic acid. Thev upper limitjof` the current densityis determined by either that density at which the conditions.

Theinvention is. further illustrated' bythe following examples but it isto beunderstood that l the inventionis not 'restricted thereto.

, A recording solution is prepared by the method *previously indicatedfrom .03 gram mol of benzi- "dine-disulfonic acid, .0104 gram mol ofben-4 -Zoyl Hjacid, .88, gramlmol'of sodium hydroxide (2.5 Ns'oluti'on).39 gram mol of sodium chloride, .035 gram molofgdiacetoacetyl ethylenediamine, .0526 gram ymol'of thi'oure'a,.l'39 gram mol of sodium nitrite'and a literA of'water.. Paper is impregnated with this solutionland theso impregnated paper is passed through the apparatus describedA above.There is thus obtained a dark recordlon a light background whichisstorage Example II The composition is the same as in Example I exceptthat there is added to the composition .5 gram per liter of the wettingagent obtained b-y condensing benzene sulfonic acid with chlorinatedkerosene.

Example III The procedure is the same as in Example I excepting thatthere is employed .0273 gram mol of benzidine-3-3'-disulfonic acid,.0094 gram mol of benzoyl H acid and .05 gram mol of diacetoacetylethylene diamine.

Example IV The procedure is the same as in Example I excepting thatthere is employed .025 gram mol of benzidine-3-3-disulfonic acid, .022gram mol of benzoyl H acid and .0292 gram mol of `diacetoacetyl ethylenediamine.

In each of the above examples, the recorded color is a sufliciently darkone to give good contrast on a yellow tinted background.

Example V The procedure is the same as in Example I excepting that thebenzoyl H acid is replaced by an equivalent amount ofbenZoyl-p-amino-benzoylI-Iacid.

The procedure is the sameas in Example excepting vthat the diacetoacetylethylene diamine is replaced by auf-equivale t amount of diacetoacetyliefopylerdiemmQ-f i ffexgmpzevrr Y Thelprocedure is: the same asinExample I ex- Lceptin'g' that the vdiacetoacetyl ethylene diamine 'ligrepla'ce'drby an equivalent amountv of diacetovacetyl .diethylenetriamine. VMTI claim: f v

l. Aprocessvof 4producing colored image rec- '.oi'dsfsimulati-ng:blackon a light background on :aA traveling carrier whichrfcomprisestreating the carrier with an alkaline solutio'ricontaining as its`essential' components `benzidinea'i.3'disulionic 'f acid Tin' an amountranging from .02 to .036 gram Amol per liter of solution, an alkalimetal nitrite :ma sufficient amount to effect tetrazotization of the`benzidine-B-disulfonic acid, a neutral elec'- trolyte in a sufficientquantity to lfacilitate the Apassage of the electrolyzing current, andas coupling components .0292 to'.05 gram mol per liter of solution ofadiacetoacetyl alkylene polyamine Vand '.0094 to .020 gram. mol per'liter` of solution of a compound ofl thef following formula: i

in which X is selected from the class consisting of hydrogen, acylamino,alkoxy, alkyl, halogen and aryloxy, and subjecting the treated carrierto the action of an electrolytic recording current.

2. The process as defined in claim 1 in which the solution Vincludesanaliphatic thioamide for .the purpose of increasing the darkness oftherecorded color. 'Y

3. ATheproess as dened in claim 1 in which thesolution includes awetting agent for facili- -tatingjcthe applicationv ofthe solution to`the carrier.

4. The process of producing colored images on a traveling carrier, saidimages having a bluegray color simulating black on a light background,which comprises treating the carrier with au alkaline solutioncont-aiming as its essential components and per liter of solution .020to .036 gram mol of benzidine-3.3disulfonic acid, from .0094 to .020gram mol of a compound of the following formula:

HOaS- SOsH 0 and subjecting the so-treated carrier to the action of anelectrolytic recording current.

5. The process as defined in claim 4 in which there is present in thesolution from .02 to .0526 gram mol of an aliphatic compound containinga thioamide group.

6. The process de'ned in claim 4 in which there is present thefsltienfrom .02 to .0526 eiaelmelfeffthouseaf r, v l.

' 7 @recess-Hof Reducing'feleredfimegeS-en Blue-'gray simulating blackonyaliglitfbaclgnound which comprises treating the carrier with anaqueous solution c'ortairii'rigas its essential com- '.penentsandmer1li-termis solution ,Y :02'lf3ig1fam mol Y :cfggbenzidine-.Sg-disultenic acid,l 5.0095 gram Emol ethylene diamine, .39gnamgmolof sodium ch1o/ ride, .139 gram mol Yof sodium nitrite;5andp.0526 e,gram@nel of :th-iourea andzsucient sodium vhy-Ydioxidetoigive arPI-I of eitoqttifandsubjecting the :treated carrier5toA tl-1e I action Iof :an electrolytic .recording current.: A 1 f8.1(Aiflbmus @sheet -rrleterial for .the electrolytic t rmationthereonyoftzo :dye-'records simulating gl-)lack ona light background, .saidsheet material fbeingv treated with-:em `aqueous alkaline solution f`containingv as =.its essential components vbenzi- .gdineg-Sdisulfonicacid in` an Y amount ranging fimmvlozfto 036-gfra1n-molper liter'of'zsolutiom a watersoluble :metallic nitrite -in :a vsufficient p,

tamount effectYtetrazotization of said :benzidine-rSfdisulfonicyacid, -alneutral electrolyte in an amountisucient'to acili-tatefthe passage cfthe electrolytic recording current and as thecoupling components .0292Sto E05 gram mol per liter of solution of Ld'acetoaxietyl' alkylenerpolyamine and .0094 to .020g-ram`mol per literA of solution of acompound ofthe following formula:

'ein s' s'ieete'affromthefeiasseonsiungof Mydregemecyiammo;aikoxygf-aikyi, halogen and aryloxy i aereas Lsnee',t Smart@nalfasennedenf daim eene@ Y -ing :Ltl'iereoncoloreirecords.'simulatingfllak nl`.aQliglfltbackgrciintltnicontairiinerlasQitsegssentizil 1 Af'nbmussheet material treated with aqueous solution capable ofletrolyticalllylyilfd] ving V,thereon colored records simulating lacklcmlalliglit` background and co1tainingV as its vessential :Name j ySolomon Dec. 20,@942

,Date Y

